2006 Vol. 23, No. 3
2006, 23(3): 1-4.
Abstract:
High temperature biphenyl polyimide resin endcapped with phenylethynyl was prepared using the modified polymerization monomeric reactant s method (MPMR) . The polyimide composite was fabricated by press molding , and the processing technique was discussed also. The polyimide composite shows high thermal stability at371 ℃. The mechanical properties of the composite at 371 ℃can maintain as much as 50 % of mechanical propertiesat room temperature. The glass t ransition temperature of the polyimide composite is 449 ℃. The mass loss at 371 ℃in air is less than 3 % over 100 h at 371 ℃. The obtained polyimide composite achieves the basic demands of the hightemperature resin at 371 ℃.
High temperature biphenyl polyimide resin endcapped with phenylethynyl was prepared using the modified polymerization monomeric reactant s method (MPMR) . The polyimide composite was fabricated by press molding , and the processing technique was discussed also. The polyimide composite shows high thermal stability at371 ℃. The mechanical properties of the composite at 371 ℃can maintain as much as 50 % of mechanical propertiesat room temperature. The glass t ransition temperature of the polyimide composite is 449 ℃. The mass loss at 371 ℃in air is less than 3 % over 100 h at 371 ℃. The obtained polyimide composite achieves the basic demands of the hightemperature resin at 371 ℃.
2006, 23(3): 5-9.
Abstract:
The fiber compaction curves of unidirectional fiber cloth were measured by the equipment designed by theauthors , and fitted curves were obtained using Gutowskips compaction equation. A parameter describing the compressibility was proposed. By using this parameter , several factors which affect the compressibility were studied ,including the initial fiber volume f raction , number of layers , variety of lubricated medium , way of layup and the variety of fiber. The result s show that the initial fiber volume f raction , number of layers and variety of lubricatedmedium have no remarkable effect s on the compressibility of the unidirectional fiber cloth. The state of whetherfibers are lubricated , the way of layup and the variety of fiber influence the compressibility significantly.
The fiber compaction curves of unidirectional fiber cloth were measured by the equipment designed by theauthors , and fitted curves were obtained using Gutowskips compaction equation. A parameter describing the compressibility was proposed. By using this parameter , several factors which affect the compressibility were studied ,including the initial fiber volume f raction , number of layers , variety of lubricated medium , way of layup and the variety of fiber. The result s show that the initial fiber volume f raction , number of layers and variety of lubricatedmedium have no remarkable effect s on the compressibility of the unidirectional fiber cloth. The state of whetherfibers are lubricated , the way of layup and the variety of fiber influence the compressibility significantly.
2006, 23(3): 10-14.
Abstract:
Impregnation behavior of fluids across the unidirectional weave stacks in the t ransverse direction of fibersunder vacuum pressure was investigated elementally by using self-designed tools , and parameters of the operationalmethod were standardized by a series of experiment s. The impregnation properties of distilled water , phenol aldehyde solution , and glycerol in carbon fiber weave stacks were studied by changing the vacuum pressures. The result sshow that the impregnation velocity of fluids improves with increasing the vacuum pressure applied. Under the samevacuum pressure , the impregnation velocity of the distilled water is the fastest . The impregnation velocity of theglycerol is faster than that of the phenol aldehyde solution at 5 kPa and 20 kPa vacuum pressure , while the phenolaldehyde solution is faster than the glycerol at 40 kPa and 60 kPa.
Impregnation behavior of fluids across the unidirectional weave stacks in the t ransverse direction of fibersunder vacuum pressure was investigated elementally by using self-designed tools , and parameters of the operationalmethod were standardized by a series of experiment s. The impregnation properties of distilled water , phenol aldehyde solution , and glycerol in carbon fiber weave stacks were studied by changing the vacuum pressures. The result sshow that the impregnation velocity of fluids improves with increasing the vacuum pressure applied. Under the samevacuum pressure , the impregnation velocity of the distilled water is the fastest . The impregnation velocity of theglycerol is faster than that of the phenol aldehyde solution at 5 kPa and 20 kPa vacuum pressure , while the phenolaldehyde solution is faster than the glycerol at 40 kPa and 60 kPa.
2006, 23(3): 15-19.
Abstract:
The effect s of non-woven nanofibrous membranes as interlaminar interfaces on the mechanical performance of laminated composites were investigated. The nanofibers were prepared by elect rospinning of Epoxy 609( E-03) . Morphology and geomet ry of the nanofibers were analyzed by SEM and TEM , and the mechanical behaviorof the non2wovens was understood through tensile testing. The non-woven fabrics were incorporated into the interlaminar interfaces of lamina plies before curing. The mechanical properties of the cured panels were measured usingthree2point flexure and short-beam test s. The result s show that the mechanical performance of the composite laminates only has a little variation when a proper thickness of nanofiber nonwovens was used. Thus , a new type offunctional composite can be manufactured by this method.
The effect s of non-woven nanofibrous membranes as interlaminar interfaces on the mechanical performance of laminated composites were investigated. The nanofibers were prepared by elect rospinning of Epoxy 609( E-03) . Morphology and geomet ry of the nanofibers were analyzed by SEM and TEM , and the mechanical behaviorof the non2wovens was understood through tensile testing. The non-woven fabrics were incorporated into the interlaminar interfaces of lamina plies before curing. The mechanical properties of the cured panels were measured usingthree2point flexure and short-beam test s. The result s show that the mechanical performance of the composite laminates only has a little variation when a proper thickness of nanofiber nonwovens was used. Thus , a new type offunctional composite can be manufactured by this method.
2006, 23(3): 20-24.
Abstract:
The effect s of compound ult rafine fibrous membranes as interlaminar interfaces on the mechanicalperformances of laminated composites were investigated. The compound ult rafine fibers were prepared by cO2axialelect rospinning of Epoxy 609 ( E-03 609) and SiC solutions. The morphology and microst ructure of the compoundult rafine fibers were analyzed with scanning elect ron microscope ( SEM) and t ransmission elect ron microscopy( TEM) , and the mechanical behavior of the membranes was studied through tensile testing. The non2woven nanofibrous membranes were incorporated into the interlaminar interfaces in between adjacent plies of the laminatesbefore curing. The mechanical properties of the cured laminate panels were measured through three-point bending ,short-beam shearing and lateral impact test s. The result s show that the mechanical performances of the compositelaminates do not change remarkably when the interfacial nanofibrous membranes have a proper thickness and asuitable content of SiC.
The effect s of compound ult rafine fibrous membranes as interlaminar interfaces on the mechanicalperformances of laminated composites were investigated. The compound ult rafine fibers were prepared by cO2axialelect rospinning of Epoxy 609 ( E-03 609) and SiC solutions. The morphology and microst ructure of the compoundult rafine fibers were analyzed with scanning elect ron microscope ( SEM) and t ransmission elect ron microscopy( TEM) , and the mechanical behavior of the membranes was studied through tensile testing. The non2woven nanofibrous membranes were incorporated into the interlaminar interfaces in between adjacent plies of the laminatesbefore curing. The mechanical properties of the cured laminate panels were measured through three-point bending ,short-beam shearing and lateral impact test s. The result s show that the mechanical performances of the compositelaminates do not change remarkably when the interfacial nanofibrous membranes have a proper thickness and asuitable content of SiC.
2006, 23(3): 25-30.
Abstract:
Theγ-ray radiation was used to modify the surface activity of pitch carbon fiber to improve the interfacialadhesion between the fiber and mat rix. The surface st ructures of the unt reated and t reated pitch carbon fibers wereinvestigated by AFM and XPS , and the measurement s of contact angles were used to understand the change of thesurface energy of the pitch carbon fibers. The effect s of γ-ray radiation on mechanical properties of the carbon/ carbon composites were investigated. The result s show thatγ-ray radiation increases the carbonyl functional group andthe surface roughness , improves the impregnation of the carbon fibers , decreases the composites porosity , andenhances the mechanical properties of composites.
Theγ-ray radiation was used to modify the surface activity of pitch carbon fiber to improve the interfacialadhesion between the fiber and mat rix. The surface st ructures of the unt reated and t reated pitch carbon fibers wereinvestigated by AFM and XPS , and the measurement s of contact angles were used to understand the change of thesurface energy of the pitch carbon fibers. The effect s of γ-ray radiation on mechanical properties of the carbon/ carbon composites were investigated. The result s show thatγ-ray radiation increases the carbonyl functional group andthe surface roughness , improves the impregnation of the carbon fibers , decreases the composites porosity , andenhances the mechanical properties of composites.
2006, 23(3): 31-36.
Abstract:
Different silicon coupling agents ( SCA) cause a large difference in mechanical properties of the glassfiber reinforced MC nylon ( GFRMCN) . The KH-570 SCA makes them decrease while the KH-550 makes themimprove. There is a rational formula between the mass f ractions of KH-550 and glass fiber. When the mass f ractionof KH-550 is 0. 2 % , the bend st rength , bend modulus , tensile st rength , tensile st ress and impact st rength ofGFRMCN are increased by 35 % , 72 % , 46 % , 88 % and 41 % , compared with those of MC nylon. Glass fibers af tersurface t reatment with KH-550 SCA increase the properties of GFRMCN because of a good interface between GFand nylon. However , most glass fibers are drawn out f rom nylon basement if they are not t reated with SCA. Theinterfaces of GF/ nylon become fatal weakness and reduce the properties of GFRMCN.
Different silicon coupling agents ( SCA) cause a large difference in mechanical properties of the glassfiber reinforced MC nylon ( GFRMCN) . The KH-570 SCA makes them decrease while the KH-550 makes themimprove. There is a rational formula between the mass f ractions of KH-550 and glass fiber. When the mass f ractionof KH-550 is 0. 2 % , the bend st rength , bend modulus , tensile st rength , tensile st ress and impact st rength ofGFRMCN are increased by 35 % , 72 % , 46 % , 88 % and 41 % , compared with those of MC nylon. Glass fibers af tersurface t reatment with KH-550 SCA increase the properties of GFRMCN because of a good interface between GFand nylon. However , most glass fibers are drawn out f rom nylon basement if they are not t reated with SCA. Theinterfaces of GF/ nylon become fatal weakness and reduce the properties of GFRMCN.
2006, 23(3): 37-43.
Abstract:
A single-layer absorber st ructure containing randomly dist ributed discrete macro-inclusions was designedby isolating the conductive medium in the absorbing mat rix , and the effects of carbon black (CB) content and samplethickness on the reflection loss as well as microwave loss mechanism were analyzed. The test results show that ,with increasing the carbon black content of the discrete particles in the slab absorber , the reflection loss increases ina f requency range of 8～18 GHz. When the mass f raction of CB get s to 30 % , the reflection loss was above - 10 dBin 8. 5～18 GHz and above - 15 dB in 15～18 GHz. Especially , when the thickness of the discrete slab absorberreaches 20 mm , the reflection loss was above - 15 dB in 8～18 GHz. The result s indicate that the discrete st ructureexhibit s the optimum absorptivity in 8～18 GHz compared with that of the compact sample , and it is a potentialexcellent absorber.
A single-layer absorber st ructure containing randomly dist ributed discrete macro-inclusions was designedby isolating the conductive medium in the absorbing mat rix , and the effects of carbon black (CB) content and samplethickness on the reflection loss as well as microwave loss mechanism were analyzed. The test results show that ,with increasing the carbon black content of the discrete particles in the slab absorber , the reflection loss increases ina f requency range of 8～18 GHz. When the mass f raction of CB get s to 30 % , the reflection loss was above - 10 dBin 8. 5～18 GHz and above - 15 dB in 15～18 GHz. Especially , when the thickness of the discrete slab absorberreaches 20 mm , the reflection loss was above - 15 dB in 8～18 GHz. The result s indicate that the discrete st ructureexhibit s the optimum absorptivity in 8～18 GHz compared with that of the compact sample , and it is a potentialexcellent absorber.
2006, 23(3): 44-48.
Abstract:
Alkylammonium ion was used to dispose sodium type montmorillonite (Na-MMT) to prepare organicmontmorillonite (OMMT) . Montmorillonite/ poly(acrylic acid) (MMT/ PAA) nanocomposites were synthesized bythe method of intercalation. The st ructure of the nanocomposite was characterized by FTIR and X-ray diff raction.The effect s of the amount of OMMT , initiator , crosslinker and size of nanocomposites on the absorbency of nanocomposites were investigated. The result s show that the intercalation is successful. Montmorillonite disperses in copolymer molecules at nano size af ter copolymerization and the absorbency of the nanocomposite is much higher thanthat of the pure PAA. The highest absorbencies of nanocomposites for distilled water and saline water are 1200 g·g-1and 121 g·g -1 , respectively.
Alkylammonium ion was used to dispose sodium type montmorillonite (Na-MMT) to prepare organicmontmorillonite (OMMT) . Montmorillonite/ poly(acrylic acid) (MMT/ PAA) nanocomposites were synthesized bythe method of intercalation. The st ructure of the nanocomposite was characterized by FTIR and X-ray diff raction.The effect s of the amount of OMMT , initiator , crosslinker and size of nanocomposites on the absorbency of nanocomposites were investigated. The result s show that the intercalation is successful. Montmorillonite disperses in copolymer molecules at nano size af ter copolymerization and the absorbency of the nanocomposite is much higher thanthat of the pure PAA. The highest absorbencies of nanocomposites for distilled water and saline water are 1200 g·g-1and 121 g·g -1 , respectively.
2006, 23(3): 49-53.
Abstract:
Thermoplastic polyimide ( TPI) composites modified by rigidity glass fillers , such as glass fiber , glassfiber powder , 5μm and 20μm glass beads , were prepared by hot-pressing. The material t ribological performanceswere measured by MPX-2000 tribo-tester , and the effect s of the fillers properties , such as shapes , size and f rictionconditions including dry sliding , water and oil lubrications , were also investigated. Based on the micro-profile of theworn surface observed by SEM , the wear mechanism was determined. The result indicates that the bigger fillershave more interfaces and bond st rength with TPI , and have a lower wear rate. The water and oil can cool the systemeffectively , and spherical particles will cause the st ress concent ration easily , which can induce fatigue wear by extending and crossovering of fatigue cracks. The degree of wear increases with increasing the filler size , so 20μm glassbead filled TPI composite has the highest wear rate under the water and oil lubrication.
Thermoplastic polyimide ( TPI) composites modified by rigidity glass fillers , such as glass fiber , glassfiber powder , 5μm and 20μm glass beads , were prepared by hot-pressing. The material t ribological performanceswere measured by MPX-2000 tribo-tester , and the effect s of the fillers properties , such as shapes , size and f rictionconditions including dry sliding , water and oil lubrications , were also investigated. Based on the micro-profile of theworn surface observed by SEM , the wear mechanism was determined. The result indicates that the bigger fillershave more interfaces and bond st rength with TPI , and have a lower wear rate. The water and oil can cool the systemeffectively , and spherical particles will cause the st ress concent ration easily , which can induce fatigue wear by extending and crossovering of fatigue cracks. The degree of wear increases with increasing the filler size , so 20μm glassbead filled TPI composite has the highest wear rate under the water and oil lubrication.
2006, 23(3): 54-59.
Abstract:
SiO2 / cyanate ester (CE) nano-composites were prepared by a high-speed homogeneous shearing method ;the quasi-static and dynamic mechanical properties and the thermal stability of the composites were investigated. Theresult s show that the impact and flexural st rengths of the composites obviously increase at the low content of SiO2 .The impact st rength reaches a maximum at 0. 30 wt % SiO2 , which is 88. 9 % higher than that of the pure CE. Andthe flexural st rength reaches a maximum at 0. 15 wt % SiO2 , which is 20 % higher than that of the pure CE. Thestorage modulus and high temperature loss modulus of the composites obviously increase compared with those of thepure CE , and the glass t ransition temperature is 31. 2 ℃ higher than that of the pure CE. It is also found that thedecomposition temperature of the composites reaches a maximum at 0. 30 wt % SiO2 ; when the mass loss of composites is 10 % , the degradation temperature increased by 25. 7 ℃compared with that of the pure CE.
SiO2 / cyanate ester (CE) nano-composites were prepared by a high-speed homogeneous shearing method ;the quasi-static and dynamic mechanical properties and the thermal stability of the composites were investigated. Theresult s show that the impact and flexural st rengths of the composites obviously increase at the low content of SiO2 .The impact st rength reaches a maximum at 0. 30 wt % SiO2 , which is 88. 9 % higher than that of the pure CE. Andthe flexural st rength reaches a maximum at 0. 15 wt % SiO2 , which is 20 % higher than that of the pure CE. Thestorage modulus and high temperature loss modulus of the composites obviously increase compared with those of thepure CE , and the glass t ransition temperature is 31. 2 ℃ higher than that of the pure CE. It is also found that thedecomposition temperature of the composites reaches a maximum at 0. 30 wt % SiO2 ; when the mass loss of composites is 10 % , the degradation temperature increased by 25. 7 ℃compared with that of the pure CE.
2006, 23(3): 60-66.
Abstract:
The biodegradable composites made f rom bagasse fibre and biodegraded resin were prepared by pressforming , and the effect s of alkali t reatment s on the fibres and composites were investigated. Compared with 3 % and5 % alkali solution , the composites reinforced with 1 % alkali solution t reated fibre show maximum improvement inmechanical properties. Af ter alkali t reatment , the fibrillation occurs and the surface of the fibres get s finer , whichcont ributes to the improvement of fibre2mat rix adhesion , and result s in enhancing the mechanical properties of composites. Furthermore , the increase of st rength and aspect ratio and the reduction of defect concent ration in the t reated fibres also improve the properties. In comparison with the unt reated composites , approximately 13 % improvement in tensile st rength , 14 % in flexural st rength and 30 % in impact st rength have been found , respectively. SEMobservations on the f racture surface of the composites show that the fibre-mat rix adhesion is improved af ter alkalit reatment s.
The biodegradable composites made f rom bagasse fibre and biodegraded resin were prepared by pressforming , and the effect s of alkali t reatment s on the fibres and composites were investigated. Compared with 3 % and5 % alkali solution , the composites reinforced with 1 % alkali solution t reated fibre show maximum improvement inmechanical properties. Af ter alkali t reatment , the fibrillation occurs and the surface of the fibres get s finer , whichcont ributes to the improvement of fibre2mat rix adhesion , and result s in enhancing the mechanical properties of composites. Furthermore , the increase of st rength and aspect ratio and the reduction of defect concent ration in the t reated fibres also improve the properties. In comparison with the unt reated composites , approximately 13 % improvement in tensile st rength , 14 % in flexural st rength and 30 % in impact st rength have been found , respectively. SEMobservations on the f racture surface of the composites show that the fibre-mat rix adhesion is improved af ter alkalit reatment s.
2006, 23(3): 67-70.
Abstract:
Cross-linked shape-stabilized phase change materials (STPCM) with different gel content s were preparedwith high-density polyethylene ( HDPE) and 1∶1 blend of HDPE and low-density polyethylene (LDPE) as mat rices.The relationship between the gel content of the materials and the content of the cross-linker-dicumyl peroxide (DCP)was discussed. The stabilities of the materials were investigated by circulation experiment s. The thermal propertiesof the cross-linked STPCM were measured by DSC. The result shows that cross-linking can improve the stability ofSTPCM with the formation of the network , which will prevent the paraffin from diffusing to the out side. HDPE/LDPE blend is more suitable to encapsulate the phase change materials than HDPE. The phase change temperatureand phase change heat will not be influenced by the gel extent . The addition of porous filler , for example , diatomite , can improve the stability of the material further.
Cross-linked shape-stabilized phase change materials (STPCM) with different gel content s were preparedwith high-density polyethylene ( HDPE) and 1∶1 blend of HDPE and low-density polyethylene (LDPE) as mat rices.The relationship between the gel content of the materials and the content of the cross-linker-dicumyl peroxide (DCP)was discussed. The stabilities of the materials were investigated by circulation experiment s. The thermal propertiesof the cross-linked STPCM were measured by DSC. The result shows that cross-linking can improve the stability ofSTPCM with the formation of the network , which will prevent the paraffin from diffusing to the out side. HDPE/LDPE blend is more suitable to encapsulate the phase change materials than HDPE. The phase change temperatureand phase change heat will not be influenced by the gel extent . The addition of porous filler , for example , diatomite , can improve the stability of the material further.
2006, 23(3): 71-76.
Abstract:
A series of organic/ inorganic hybrids involving epoxy resin and t riethoxysilane-terminated polycaprolactone elastomer ( PCL-TESi) were prepared via polymerization of diglycidyl ether of bisphenol A (DGEBA) withamine curing agent KB-2 and sol-gel process of PCL-TESi. The organic/ inorganic hybrids were characterized byFT-IR , transmission elect ron microscopy ( TEM) , thermogravimetry analysis ( TGA) and swelling in toluene. Theresult s show that the swelling property in toluene , morphologies and thermal degradation of the hybrids are quitedependent on the content of PCL-TESi. The crosslink network density decreases with increasing of the PCL-TESi.And in TEM , the phase separation morphology of these hybrids is found , which resulted f rom the coagulation ofSi —O —Si networks and the curing reaction of the epoxy resin system. Meanwhile , the size of each phase is in nanoscale. And in TG analysis , the characteristic decomposition temperature at 5 % weight loss is evidently increasedf rom 120. 5 ℃of pure cured epoxy to 277. 6 ℃of 3. 84 % SiO2 modified epoxy ; this is due to the existence of Si —O —Si when PCL2TESi is added in the hybrid.
A series of organic/ inorganic hybrids involving epoxy resin and t riethoxysilane-terminated polycaprolactone elastomer ( PCL-TESi) were prepared via polymerization of diglycidyl ether of bisphenol A (DGEBA) withamine curing agent KB-2 and sol-gel process of PCL-TESi. The organic/ inorganic hybrids were characterized byFT-IR , transmission elect ron microscopy ( TEM) , thermogravimetry analysis ( TGA) and swelling in toluene. Theresult s show that the swelling property in toluene , morphologies and thermal degradation of the hybrids are quitedependent on the content of PCL-TESi. The crosslink network density decreases with increasing of the PCL-TESi.And in TEM , the phase separation morphology of these hybrids is found , which resulted f rom the coagulation ofSi —O —Si networks and the curing reaction of the epoxy resin system. Meanwhile , the size of each phase is in nanoscale. And in TG analysis , the characteristic decomposition temperature at 5 % weight loss is evidently increasedf rom 120. 5 ℃of pure cured epoxy to 277. 6 ℃of 3. 84 % SiO2 modified epoxy ; this is due to the existence of Si —O —Si when PCL2TESi is added in the hybrid.
2006, 23(3): 77-81.
Abstract:
The AC/ Ni-Co composite elect rode was prepared by means of composite-elect rodeposition. The surfacemorphology and microst ructure of the elect rode coating were observed by XRD and SEM. The result s show that thecomposition of AC does not change the crystal st ructure of the Ni-Co alloy elect rode , but the surface roughness andreal surface area of the coatings increase. Catalytic abilities for hydrogen evolution of different elect rodes in1 mol·L-1 NaOH solution were evaluated on the basis of elect rochemical steady-state polarization curves andalternating current impedance spect rum technology. The result s show that the AC/ Ni-Co composite elect rode ( theamount of AC is 3 g·L-1 in bath ) is catalytically more active than the Ni and Ni-Co alloy elect rode. The polarizationpotential for hydrogen evolution of the composite elect rode is 230 mV lower than that of the Ni elect rode and is140 mV lower than that of the Ni-Co alloy elect rode at the current density of 0. 03 A·cm-2 . The apparent exchangecurrent density of the composite elect rode is 30 times as much as that of Ni elect rode , and 6 times that of the Ni-Coalloy elect rode. The increasing catalytic activity for hydrogen evolution of the AC/ Ni-Co composite elect rode ismainly due to the increase in the real surface area of the elect rode.
The AC/ Ni-Co composite elect rode was prepared by means of composite-elect rodeposition. The surfacemorphology and microst ructure of the elect rode coating were observed by XRD and SEM. The result s show that thecomposition of AC does not change the crystal st ructure of the Ni-Co alloy elect rode , but the surface roughness andreal surface area of the coatings increase. Catalytic abilities for hydrogen evolution of different elect rodes in1 mol·L-1 NaOH solution were evaluated on the basis of elect rochemical steady-state polarization curves andalternating current impedance spect rum technology. The result s show that the AC/ Ni-Co composite elect rode ( theamount of AC is 3 g·L-1 in bath ) is catalytically more active than the Ni and Ni-Co alloy elect rode. The polarizationpotential for hydrogen evolution of the composite elect rode is 230 mV lower than that of the Ni elect rode and is140 mV lower than that of the Ni-Co alloy elect rode at the current density of 0. 03 A·cm-2 . The apparent exchangecurrent density of the composite elect rode is 30 times as much as that of Ni elect rode , and 6 times that of the Ni-Coalloy elect rode. The increasing catalytic activity for hydrogen evolution of the AC/ Ni-Co composite elect rode ismainly due to the increase in the real surface area of the elect rode.
2006, 23(3): 82-86.
Abstract:
Na-montmorillonite (Na2MMT) was exchanged with Cu2+ and t ributyltet radecyl phosphonium cation( TBTP) in turn by the ion2exchange method. The mass f ractions of TBTP and Cu2+ were 24. 07 % and 2. 87 % ,respectively. The result s of TG and XRD show that Cu2+ and TBTP have been exchanged in montmorillonite , andthe onset decomposition temperature of the quaternary phosphonium cation is about 220 ℃. The antimicrobial experiment indicates that the montmorillonite composite materials ( TBTP-Cu/ MMT) possess wonderful antimicrobialactivity and the minimal inhibitory concent rations (MIC) are 12. 5μg·mL-1 and 200μg·mL-1 against S. aureus andE. col i , respectively. The influences of the concent ration of TBTP-Cu/ MMT and contacting time with bacteria onthe antimicrobial activity of the modified montmorillonite were studied. The result indicates that their antimicrobialactivities increase with increasing the concent ration and contacting time with bacteria. After 100 mg TBTP-Cu/MMT being soaked in water for 20 days , the release amount s of TBTP and Cu2+ f rom the montmorillonite composite materials are only 41891 mg·L-1 and 1. 928 mg·L-1 , respectively.
Na-montmorillonite (Na2MMT) was exchanged with Cu2+ and t ributyltet radecyl phosphonium cation( TBTP) in turn by the ion2exchange method. The mass f ractions of TBTP and Cu2+ were 24. 07 % and 2. 87 % ,respectively. The result s of TG and XRD show that Cu2+ and TBTP have been exchanged in montmorillonite , andthe onset decomposition temperature of the quaternary phosphonium cation is about 220 ℃. The antimicrobial experiment indicates that the montmorillonite composite materials ( TBTP-Cu/ MMT) possess wonderful antimicrobialactivity and the minimal inhibitory concent rations (MIC) are 12. 5μg·mL-1 and 200μg·mL-1 against S. aureus andE. col i , respectively. The influences of the concent ration of TBTP-Cu/ MMT and contacting time with bacteria onthe antimicrobial activity of the modified montmorillonite were studied. The result indicates that their antimicrobialactivities increase with increasing the concent ration and contacting time with bacteria. After 100 mg TBTP-Cu/MMT being soaked in water for 20 days , the release amount s of TBTP and Cu2+ f rom the montmorillonite composite materials are only 41891 mg·L-1 and 1. 928 mg·L-1 , respectively.
2006, 23(3): 87-90.
Abstract:
In order to research new environmental acoustic materials , the piezoelect ric , elect ric conduction andacoustic absorption composite was prepared by dispersing the carbon black powder (CB) into the polyvinyl chloride( PVC) mat rix with lead zirconate titanate ( PZT) on the basis of piezoelect ricity and elect rical conductivity theory.The dynamic mechanical , elect ric and acoustic properties of the composite were measured and analyzed. The energydissipation mechanism of piezoelect ric and acoustic absorption route of the composite were studied. The result s showthat the acoustic absorption property of the piezoelect ric and elect ric conduction composite reaches the highest valuewhen the volume f raction of carbon black is 4 %.
In order to research new environmental acoustic materials , the piezoelect ric , elect ric conduction andacoustic absorption composite was prepared by dispersing the carbon black powder (CB) into the polyvinyl chloride( PVC) mat rix with lead zirconate titanate ( PZT) on the basis of piezoelect ricity and elect rical conductivity theory.The dynamic mechanical , elect ric and acoustic properties of the composite were measured and analyzed. The energydissipation mechanism of piezoelect ric and acoustic absorption route of the composite were studied. The result s showthat the acoustic absorption property of the piezoelect ric and elect ric conduction composite reaches the highest valuewhen the volume f raction of carbon black is 4 %.
2006, 23(3): 91-95.
Abstract:
0-3 cement based piezoelect ric composites were fabricated using sulphoaluminate cement and piezoelect ricceramic [0.08Pb (Li1/4 Nb3/4 ) O3 ·0. 47PbTiO3 ·0. 45PbZrO3 ] as raw materials. The phase component s and micrO2st ructures of the composites were analyzed by XRD and SEM. The dielectric f requency characteristics and ferroelectriccharacteristics of the composites were mainly investigated. The results indicate that the bonding between piezoelectricceramic particle and hydration product s of sulphoaluminate cement is good. With increasing the PLN content , thedielect ric constantεr , remanent polarization Pr and coercive field Ec increase. The dielectric constant decreases sharplywith f requency increasing over the f requency ranges f rom 40 kHz to 100 kHz , which is att ributed to interfacialpolarization in the composite. At high f requency , the dielect ric constant changes slightly , which means that thecement-based piezoelect ric composites have good high f requency stability. The reasons why the hysteresis loopsdistort are mainly that there are both many defect s in the piezoelect ric ceramic particles af ter breaking and manyinterfacial pores in the composites.
0-3 cement based piezoelect ric composites were fabricated using sulphoaluminate cement and piezoelect ricceramic [0.08Pb (Li1/4 Nb3/4 ) O3 ·0. 47PbTiO3 ·0. 45PbZrO3 ] as raw materials. The phase component s and micrO2st ructures of the composites were analyzed by XRD and SEM. The dielectric f requency characteristics and ferroelectriccharacteristics of the composites were mainly investigated. The results indicate that the bonding between piezoelectricceramic particle and hydration product s of sulphoaluminate cement is good. With increasing the PLN content , thedielect ric constantεr , remanent polarization Pr and coercive field Ec increase. The dielectric constant decreases sharplywith f requency increasing over the f requency ranges f rom 40 kHz to 100 kHz , which is att ributed to interfacialpolarization in the composite. At high f requency , the dielect ric constant changes slightly , which means that thecement-based piezoelect ric composites have good high f requency stability. The reasons why the hysteresis loopsdistort are mainly that there are both many defect s in the piezoelect ric ceramic particles af ter breaking and manyinterfacial pores in the composites.
Preparation and properties of nano electrorheological fluid ofmodif ied titanium oxide nano particle
2006, 23(3): 96-102.
Abstract:
Acrylamide modified titanium oxide nano particles were prepared by combining the modified hydrolysisand solution deposition methods , using sodium dodecylbenzene sulphonate (SDBS) as the dispersing agent . XRD result shows that the nano particles are amorphous , and the size dispersion ranges f rom 70 nm to 300 nm characterizedby the laser particle size analyzer. FTIR pat terns show that acrylamide and SDBS are adsorbed on the surface of titanium oxide particles. The addition of SDBS affect s the size and the surface characterization of particles , and the wettability between particles and silicone oil , which sequentially leads to the improvement of dielect ric property. Anexcellent elect rorheological activity has been found when the nano particles are dispersed into the silicone oil. Underan elect ric field of 5 kV/ mm , the shear st ress will reach 90 kPa , when the mass f ractions of acrylamide and SDBS are1. 875 % and 0. 750 % , respectively. The ERF also shows very good dispersion stability.
Acrylamide modified titanium oxide nano particles were prepared by combining the modified hydrolysisand solution deposition methods , using sodium dodecylbenzene sulphonate (SDBS) as the dispersing agent . XRD result shows that the nano particles are amorphous , and the size dispersion ranges f rom 70 nm to 300 nm characterizedby the laser particle size analyzer. FTIR pat terns show that acrylamide and SDBS are adsorbed on the surface of titanium oxide particles. The addition of SDBS affect s the size and the surface characterization of particles , and the wettability between particles and silicone oil , which sequentially leads to the improvement of dielect ric property. Anexcellent elect rorheological activity has been found when the nano particles are dispersed into the silicone oil. Underan elect ric field of 5 kV/ mm , the shear st ress will reach 90 kPa , when the mass f ractions of acrylamide and SDBS are1. 875 % and 0. 750 % , respectively. The ERF also shows very good dispersion stability.
2006, 23(3): 103-107.
Abstract:
Ni-20Fe/ Al2O3 nanocomposites with high relative density (D ≥98 %) were fabricated using the mechanochemical method and the hot-pressing process. The fracture toughness is increased f rom 4. 7 to 6. 2 MPa·m1/2 asNi-20Fe volume f raction increases f rom 0 to 19 %. Both the intergranular and the t ransgranular f ractures areobserved on the f racture surface by FE-SEM. When 19 % Ni-20Fe is added , the composite Ms is 33 emu/ g , Hc is200 Oe , and Hc keep s constant below 500 ℃, which shows good magnetic heat stability.
Ni-20Fe/ Al2O3 nanocomposites with high relative density (D ≥98 %) were fabricated using the mechanochemical method and the hot-pressing process. The fracture toughness is increased f rom 4. 7 to 6. 2 MPa·m1/2 asNi-20Fe volume f raction increases f rom 0 to 19 %. Both the intergranular and the t ransgranular f ractures areobserved on the f racture surface by FE-SEM. When 19 % Ni-20Fe is added , the composite Ms is 33 emu/ g , Hc is200 Oe , and Hc keep s constant below 500 ℃, which shows good magnetic heat stability.
2006, 23(3): 108-113.
Abstract:
Using the pure NH4Al(SO4 )2·12H2O , ZrOCl2 ·8H2O and Y(NO3 ) 3 as the starting materials , and theN H4 HCO3 solution as precipitant , the ult rafine 3 Y-ZrO2 / Al2O3 precursor was prepared by the liquid-phase precipitation method. The effect s of seeds and the calcination temperature on the properties of the powder were studied.The well-dispersible ZrO2 / Al2O3 composite nanopowder with particles of 10 nm was obtained by calcining the precursor at 1000 ℃. The XRD patterns show noγ-Al2O3 andθ-Al2O3 form during calcination. The relative density andfracture toughness of specimen reach 98. 6 % and 7. 68 MPa·m1/2 , respectively af ter sintering the green compact s at1550 ℃for 3 h.
Using the pure NH4Al(SO4 )2·12H2O , ZrOCl2 ·8H2O and Y(NO3 ) 3 as the starting materials , and theN H4 HCO3 solution as precipitant , the ult rafine 3 Y-ZrO2 / Al2O3 precursor was prepared by the liquid-phase precipitation method. The effect s of seeds and the calcination temperature on the properties of the powder were studied.The well-dispersible ZrO2 / Al2O3 composite nanopowder with particles of 10 nm was obtained by calcining the precursor at 1000 ℃. The XRD patterns show noγ-Al2O3 andθ-Al2O3 form during calcination. The relative density andfracture toughness of specimen reach 98. 6 % and 7. 68 MPa·m1/2 , respectively af ter sintering the green compact s at1550 ℃for 3 h.
2006, 23(3): 114-122.
Abstract:
A new bio-composite material , graded zirconia-hydroxyapatite composite Bioceramic , has been preparedby the dry-laying & sintering method , and it s mechanical properties , microst ructure and biocompatibility have beenstudied. The powders and the composite material were investigated using SEM , XRD , TEM and EDAX. To evaluate it s biocompatibility , the ext ract of the composite material was used to carry out a mouse acute toxicity test , a cytotoxicity test , an in vit ro hemolytic test , and a rabbit muscle and bone implantation experiment . The result s showthat the coating of the composite material is about 80μm thick , and is well bonded with the core mat rix without obvious interface. The bond st rength is 15. 1 MPa , the maximum flexural st rength is 1112. 24 MPa , and KIC is 7. 3～11. 4 MPa·m1/2 . The graded zirconia2hydroxyapatite composite bioceramic has excellent biocompatibilities and boneconductivities , which can promote the growing of bone issues , so it is an ideal bio-composite material for orthopaedicimplantation.
A new bio-composite material , graded zirconia-hydroxyapatite composite Bioceramic , has been preparedby the dry-laying & sintering method , and it s mechanical properties , microst ructure and biocompatibility have beenstudied. The powders and the composite material were investigated using SEM , XRD , TEM and EDAX. To evaluate it s biocompatibility , the ext ract of the composite material was used to carry out a mouse acute toxicity test , a cytotoxicity test , an in vit ro hemolytic test , and a rabbit muscle and bone implantation experiment . The result s showthat the coating of the composite material is about 80μm thick , and is well bonded with the core mat rix without obvious interface. The bond st rength is 15. 1 MPa , the maximum flexural st rength is 1112. 24 MPa , and KIC is 7. 3～11. 4 MPa·m1/2 . The graded zirconia2hydroxyapatite composite bioceramic has excellent biocompatibilities and boneconductivities , which can promote the growing of bone issues , so it is an ideal bio-composite material for orthopaedicimplantation.
2006, 23(3): 123-126.
Abstract:
The Si3N4-SiC-TiN multiphase ceramic was synthesized f rom TiSi2 and SiC powders by self-propagatinghigh-temperature synthesis in which SiC is acting as a diluent . The effect of nit rogen pressure on the conversiondegree of the reactant was calculated in theory , and combustion synthesis was carried out under nit rogen pressuresof 50 , 100 and 150 MPa , respectively. The result s show that the green part s of 50 vol % porosity are well nit rifiedunder the three pressures , while those of 40 vol % porosity can not be nit rified completely in which agglomerate Si isfound when they were synthesized under lower pressure. However , there is no Si detected in the final product s madeby 40 vol % porosity part s under 150 MPa nit rogen pressure. Accordingly , the high nit rogen pressure is of advantage to the infilt ration of nit rogen and the increase of conversion degree.
The Si3N4-SiC-TiN multiphase ceramic was synthesized f rom TiSi2 and SiC powders by self-propagatinghigh-temperature synthesis in which SiC is acting as a diluent . The effect of nit rogen pressure on the conversiondegree of the reactant was calculated in theory , and combustion synthesis was carried out under nit rogen pressuresof 50 , 100 and 150 MPa , respectively. The result s show that the green part s of 50 vol % porosity are well nit rifiedunder the three pressures , while those of 40 vol % porosity can not be nit rified completely in which agglomerate Si isfound when they were synthesized under lower pressure. However , there is no Si detected in the final product s madeby 40 vol % porosity part s under 150 MPa nit rogen pressure. Accordingly , the high nit rogen pressure is of advantage to the infilt ration of nit rogen and the increase of conversion degree.
2006, 23(3): 127-129.
Abstract:
Bamboos , a kind of bio-materials , grow fast and have good mechanical behaviors. The properties of outside st rip of bamboo are better than those of inside , so the grading process was developed , which can make the laminate bamboo st rip lumber (LSBL) of grading A , B , C and D. The advanced biO2composites , compared with othermaterials , can replace GFRP and wood/ epoxy , and can be used in wind blades as a new generation of materials.This new materials have many advantages , such as renewable , less dissipation of energy , low cost , no waste and theworn2out product s can be disposed easily.
Bamboos , a kind of bio-materials , grow fast and have good mechanical behaviors. The properties of outside st rip of bamboo are better than those of inside , so the grading process was developed , which can make the laminate bamboo st rip lumber (LSBL) of grading A , B , C and D. The advanced biO2composites , compared with othermaterials , can replace GFRP and wood/ epoxy , and can be used in wind blades as a new generation of materials.This new materials have many advantages , such as renewable , less dissipation of energy , low cost , no waste and theworn2out product s can be disposed easily.
2006, 23(3): 130-134.
Abstract:
A numeral model of erosion for carbon-based materials impacted by hypervelocity particles was established based on dynamics. The parameters characterizing the capability of materials resistance to erosion , impactdamage erosion energy and shear damage erosion energy were int roduced in this model. The theoretical formulas ofthe volume loss caused by particles impacting were obtained by defining a multiple impact s modifying factor β. Theextent of erosion of graphite and C/ C composite was calculated while the impact angle and velocity of Al2O3 particlesvaried. The result s indicate that , although both forms of mechanical damage would take place simultaneously , themechanism of carbon-based materials appears to be the impact damage caused by normal force. The calculationresult s achieved by the present method well agree with the experimental data in the related literature.
A numeral model of erosion for carbon-based materials impacted by hypervelocity particles was established based on dynamics. The parameters characterizing the capability of materials resistance to erosion , impactdamage erosion energy and shear damage erosion energy were int roduced in this model. The theoretical formulas ofthe volume loss caused by particles impacting were obtained by defining a multiple impact s modifying factor β. Theextent of erosion of graphite and C/ C composite was calculated while the impact angle and velocity of Al2O3 particlesvaried. The result s indicate that , although both forms of mechanical damage would take place simultaneously , themechanism of carbon-based materials appears to be the impact damage caused by normal force. The calculationresult s achieved by the present method well agree with the experimental data in the related literature.
2006, 23(3): 135-140.
Abstract:
A three-dimensional finite element analysis was presented for the composite multiple bolted joint s. Theanalysis took into account the progressive damage process and non-linear contact behavior at each bolt-hole interface.The 1 ×3 bolted single-shear joint s were modeled and the final damage loads were compared with those f rom a parallel experimental research. Three sort s of T300/ Q Y9512 composite plates with different geomet ry configurationswith the single lap were tested. The model developed in this paper shows excellent capability to quantify the effectsof geomet ries , which include substantially changed load dist ribution , damage onset and development in the multiplebolted joint case. The result s show that the thickness variance does not change the bolt load st ress. However , varying the thickness of the laminate has a significant effect on the st ress value and dist ribution around the bolt .
A three-dimensional finite element analysis was presented for the composite multiple bolted joint s. Theanalysis took into account the progressive damage process and non-linear contact behavior at each bolt-hole interface.The 1 ×3 bolted single-shear joint s were modeled and the final damage loads were compared with those f rom a parallel experimental research. Three sort s of T300/ Q Y9512 composite plates with different geomet ry configurationswith the single lap were tested. The model developed in this paper shows excellent capability to quantify the effectsof geomet ries , which include substantially changed load dist ribution , damage onset and development in the multiplebolted joint case. The result s show that the thickness variance does not change the bolt load st ress. However , varying the thickness of the laminate has a significant effect on the st ress value and dist ribution around the bolt .
2006, 23(3): 141-145.
Abstract:
The buckling and postbuckling behavior of advanced grid stiffened st ructures with damage af ter impactwas investigated by numerical analysis. Based on the Mindlin first order shear effect theory and the Von Karmannon2linearity assumption , a finite element method was developed for the postbuckling behavior of the advanced gridstiffened st ructure (AGS) , considering the stiffness degradation induced by the progressive failure including fibref racture and mat rix crack. The overlap of the upper and the lower sub2laminates is overcome by a nonlinear contactelement . An effective numerical method for the postbuckling behavior of the damaged advanced grid stiffened st ructure is provided , and the conclusions obtained in this paper can be useful for the load capacity prediction of suchst ructures. The numerical result s show that the AGS st ructure still has a large load capacity af ter the local bucklingof the delaminated skin. The progressive failure analysis must be considered during the course of postbuckling analysis. Using the nonlinear contact element can avoid the overlap and penet ration phenomenon between the upper andlower sub-laminates at the delaminated region.
The buckling and postbuckling behavior of advanced grid stiffened st ructures with damage af ter impactwas investigated by numerical analysis. Based on the Mindlin first order shear effect theory and the Von Karmannon2linearity assumption , a finite element method was developed for the postbuckling behavior of the advanced gridstiffened st ructure (AGS) , considering the stiffness degradation induced by the progressive failure including fibref racture and mat rix crack. The overlap of the upper and the lower sub2laminates is overcome by a nonlinear contactelement . An effective numerical method for the postbuckling behavior of the damaged advanced grid stiffened st ructure is provided , and the conclusions obtained in this paper can be useful for the load capacity prediction of suchst ructures. The numerical result s show that the AGS st ructure still has a large load capacity af ter the local bucklingof the delaminated skin. The progressive failure analysis must be considered during the course of postbuckling analysis. Using the nonlinear contact element can avoid the overlap and penet ration phenomenon between the upper andlower sub-laminates at the delaminated region.
2006, 23(3): 146-152.
Abstract:
The axisymmet ric finite element models of the mat rix crack deflection/ penet ration for two -phase andthree-phase composites were established respectively by applying the energy-based crack deflection criterion. Theeffects of the fiber volume f raction , the Dundurs parameter αdescribing the elastic mismatch between material properties , and the relative crack growth length ad / ap on the relative energy release rate ratio Gd / Gp were investigated.The FEA result s were compared with those obtained by He for two-phase composites , and the effect s of the interphase thickness , Dundurs parametersα1 andα2 on Gd / Gp were further studied for three-phase composites. The SiCfiber-reinforced composite SiC/ C/ Ti-6Al-4V and ceramic composite SiC/ C/ SiC coated with cabon were analyzed bythe FEA respectively , and the result s show that the models can accurately predict and compare the mat rix crackdeflection mechanisms.
The axisymmet ric finite element models of the mat rix crack deflection/ penet ration for two -phase andthree-phase composites were established respectively by applying the energy-based crack deflection criterion. Theeffects of the fiber volume f raction , the Dundurs parameter αdescribing the elastic mismatch between material properties , and the relative crack growth length ad / ap on the relative energy release rate ratio Gd / Gp were investigated.The FEA result s were compared with those obtained by He for two-phase composites , and the effect s of the interphase thickness , Dundurs parametersα1 andα2 on Gd / Gp were further studied for three-phase composites. The SiCfiber-reinforced composite SiC/ C/ Ti-6Al-4V and ceramic composite SiC/ C/ SiC coated with cabon were analyzed bythe FEA respectively , and the result s show that the models can accurately predict and compare the mat rix crackdeflection mechanisms.
2006, 23(3): 153-157.
Abstract:
Some improved manufacture tooling methods for composite grid plates were presented and an interlockedcomposite grid plate has been made. Based on finite element models , considering the st ructural mechanical propertyand manufacture process , the geomet ric parameters optimizing design was studied for the composite grid plate. Theresearch and findings would be utilized to manufacture and primary design of advanced composite grids plate st ructures.
Some improved manufacture tooling methods for composite grid plates were presented and an interlockedcomposite grid plate has been made. Based on finite element models , considering the st ructural mechanical propertyand manufacture process , the geomet ric parameters optimizing design was studied for the composite grid plate. Theresearch and findings would be utilized to manufacture and primary design of advanced composite grids plate st ructures.
2006, 23(3): 158-164.
Abstract:
The smart composite material can be prepared by pre2embedding FBG sensors into CFRP laminates.Four pieces of RC beams were prepared in the experiment s , where FBG sensors and elect ric st rain gauges were preembedded in the steel , concrete and CFRP in RC beams. A numerical simulation program for flexural load effect s ofRC beams was compiled based on the theory of reinforced concrete and finite element sof tware ANSYS. The experimental result s show that during the load bearing process , the linear relationship of FBG sensor and elect ric st raingauge is uniform; the numerical simulation result s and the measuring result s of st rains in the tensile steel and thecompressive concrete , and the load vs the mid-span deflection agree well. The under-servicing RC structures are difficult to mount sensors internally (because the st ructure will be dest royed and the resistance force will be reduced) ,so utilizing the smart CFRP st rengthened RC st ructures can realize the dual function of advanced rehabilitation andreal-time health monitoring and assessing.
The smart composite material can be prepared by pre2embedding FBG sensors into CFRP laminates.Four pieces of RC beams were prepared in the experiment s , where FBG sensors and elect ric st rain gauges were preembedded in the steel , concrete and CFRP in RC beams. A numerical simulation program for flexural load effect s ofRC beams was compiled based on the theory of reinforced concrete and finite element sof tware ANSYS. The experimental result s show that during the load bearing process , the linear relationship of FBG sensor and elect ric st raingauge is uniform; the numerical simulation result s and the measuring result s of st rains in the tensile steel and thecompressive concrete , and the load vs the mid-span deflection agree well. The under-servicing RC structures are difficult to mount sensors internally (because the st ructure will be dest royed and the resistance force will be reduced) ,so utilizing the smart CFRP st rengthened RC st ructures can realize the dual function of advanced rehabilitation andreal-time health monitoring and assessing.
2006, 23(3): 165-169.
Abstract:
The microst ructure of a four-step 3D braiding preform with 1 ×1 pattern and complex rectangular crosssection was studied by means of the cont rol volume method. The complex rectangular configuration refers to the geomet rical shape jointed by two or more rectangles together. According to the formation rule of the braiding process ,the paths of the carriers are t raced , particularly in the joint region where two rectangles join together. In addition tothe microst ructures of the braiding preform in the interior , surface and corner of a simple rectangle , there are differentmicrost ructures in the joint region of the interior , surface and corner of the complex rectangle. Corresponding to thespecial microst ructure in the interior , surface and corner in the joint region , three unit cell models were developed.The result shows that , in the joint region , the geomet ry of the unit cell in the interior , corner and surface is of acube , a hepta-prism and a penta-prism , respectively. In addition , the braiding pattern and braiding angle of the unitcells in the joint region differ significantly f rom those of the simple rectangle of a 3D braiding preform.
The microst ructure of a four-step 3D braiding preform with 1 ×1 pattern and complex rectangular crosssection was studied by means of the cont rol volume method. The complex rectangular configuration refers to the geomet rical shape jointed by two or more rectangles together. According to the formation rule of the braiding process ,the paths of the carriers are t raced , particularly in the joint region where two rectangles join together. In addition tothe microst ructures of the braiding preform in the interior , surface and corner of a simple rectangle , there are differentmicrost ructures in the joint region of the interior , surface and corner of the complex rectangle. Corresponding to thespecial microst ructure in the interior , surface and corner in the joint region , three unit cell models were developed.The result shows that , in the joint region , the geomet ry of the unit cell in the interior , corner and surface is of acube , a hepta-prism and a penta-prism , respectively. In addition , the braiding pattern and braiding angle of the unitcells in the joint region differ significantly f rom those of the simple rectangle of a 3D braiding preform.
2006, 23(3): 170-175.
Abstract:
The breakage micro-mechanism of plain-woven fiber reinforced composite materials was studied by meansof t ransverse compressive and tensile experiment s. It is observed that the shear damage along 45°with the fill st randoccurs together with interlaminar cracks during the process of t ransverse compression. The damage forms of warpst rand and fill st rand are different because of the curve diversity , and the st rand interfaces and laminar interfaces atf ree-edges show different shear failures. The differences among failure models are due to the different bendingshapes of st rands. These phenomena were analysed through microscope observation and numerical simulation. Somepossible reasons were given to explain these failure forms. The main reason may be that the interlaminar shear st ressis induced by highly anomalous st rand st ructure under t ransverse compression.
The breakage micro-mechanism of plain-woven fiber reinforced composite materials was studied by meansof t ransverse compressive and tensile experiment s. It is observed that the shear damage along 45°with the fill st randoccurs together with interlaminar cracks during the process of t ransverse compression. The damage forms of warpst rand and fill st rand are different because of the curve diversity , and the st rand interfaces and laminar interfaces atf ree-edges show different shear failures. The differences among failure models are due to the different bendingshapes of st rands. These phenomena were analysed through microscope observation and numerical simulation. Somepossible reasons were given to explain these failure forms. The main reason may be that the interlaminar shear st ressis induced by highly anomalous st rand st ructure under t ransverse compression.
2006, 23(3): 176-180.
Abstract:
The physical performances of the three-dimensionally braided composite st ructure around a hole werediscussed. Three types of holes were analyzed including braided hole , compressed hole and drilled hole. The geomet rical model and physical model used in the analysis are based on the braided unit-cell. Firstly , according to themaking procedure of the three kinds of holes , the calculation of the unit-cellps geomet rical parameters was performed. Then , the unit-cellps physical parameters could be obtained by using the inclined-plate model and classiclaminate theory. Af ter gaining physical parameters of each unit-cell around holes , the finite-element method wasused to analyze the properties around this area. Some typical 3-D braided composite plates with a hole were analyzedusing the method produced above. The experiment on a typical st ructure was performed , and the result s agreed wellwith the theoretical calculation. Some rules were concluded f rom the analysis result , which can guide the design andmanufacture of 3-D braided composite st ructures with holes.
The physical performances of the three-dimensionally braided composite st ructure around a hole werediscussed. Three types of holes were analyzed including braided hole , compressed hole and drilled hole. The geomet rical model and physical model used in the analysis are based on the braided unit-cell. Firstly , according to themaking procedure of the three kinds of holes , the calculation of the unit-cellps geomet rical parameters was performed. Then , the unit-cellps physical parameters could be obtained by using the inclined-plate model and classiclaminate theory. Af ter gaining physical parameters of each unit-cell around holes , the finite-element method wasused to analyze the properties around this area. Some typical 3-D braided composite plates with a hole were analyzedusing the method produced above. The experiment on a typical st ructure was performed , and the result s agreed wellwith the theoretical calculation. Some rules were concluded f rom the analysis result , which can guide the design andmanufacture of 3-D braided composite st ructures with holes.
2006, 23(3): 181-184.
Abstract:
The Love wave behavior in magneto-elect ro-elastic multilayered st ructures was investigated. Firstly , thegeneral mechanical displacement , elect ric potential and magnetic potential were found by solving the coupled magneto-elect ro-elastic field equations. The dispersion equation of the Love wave was then derived by the propagationmat rix method , combined with the continuity condition across the interface of the layers. Numerical result s forsandwich composites made of Ba TiO3 and Co Fe2O4 were presented and discussed , including dispersion curves fordifferent stacking sequences and for different thicknesses of the middle layer.
The Love wave behavior in magneto-elect ro-elastic multilayered st ructures was investigated. Firstly , thegeneral mechanical displacement , elect ric potential and magnetic potential were found by solving the coupled magneto-elect ro-elastic field equations. The dispersion equation of the Love wave was then derived by the propagationmat rix method , combined with the continuity condition across the interface of the layers. Numerical result s forsandwich composites made of Ba TiO3 and Co Fe2O4 were presented and discussed , including dispersion curves fordifferent stacking sequences and for different thicknesses of the middle layer.
